1. Field of the Invention
This invention relates to integrated circuits and, more particularly, to level shifter circuits.
2. Description of the Related Art
Circuits such as level shifter circuits may enable signals to pass between circuits operating in different voltage domains. For example, one circuit may operate at 0.4V while another circuit may operate at 1.3V. Level shifters may have an input that can recognize signal transitions referenced to the 0.4V supply, and may provide a corresponding output signal that is referenced to the 1.3V supply. Depending on process parameters during manufacturing, it may be possible for the voltage thresholds of the level shifter circuits to vary between manufacturing lots. This variability may present reliability problems.
The manufacturing of integrated circuits is a complex process. Bringing a new circuit design to a fabrication facility, or bringing an existing circuit design to a new fabrication facility may require a number of characterization steps to establish a device library. Depending on the process technology, and the complexity of the circuits, there may be several iterations of process adjustments to ensure reliable operation of the manufactured devices. In many cases, there may be several revisions of silicon before the design is fully operational. Accordingly, it may be desirable to provide a robust circuit design while reducing the number of iterations of process adjustments, particularly during device and process characterization.